TM 10-3930-669-20 2-13.  ENGINE SYSTEM TROUBLESHOOTING (CONT). 7.  ENGINE RUNS ROUGH OR MISFIRES. INITIAL SETUP Tools and Special Tools Equipment Condition Tool Kit, General Mechanic's: Automotive Engine OFF (TM 10-3930-669-10) (Item 1, Appendix B) MAIN POWER switch OFF (TM 10-3930-669-10) Pan, Drain (Item 11, Appendix B) Parking brake applied (TM 10-3930-669-10) Wheels chocked (TM 10-3930-669-10) References TM 10-3930-669-10 KNOWN INFO Nothing. POSSIBLE PROBLEMS Contaminated fuel. Fuel lines loose or damaged. Intake/exhaust valve adjustment incorrect. Air in fuel lines. Fuel injector(s) faulty. TEST OPTIONS Visual inspection. REASON FOR QUESTION If fuel is contaminated, engine will run rough. 2-92